Modular thermoelectric-based cooling device for heterogeneous packages

ABSTRACT

A cooling device for a heterogeneous microchip is fabricated such that different cooling profiles can be provided for different chips. A housing is made of thermal conductive material, the housing having a plurality of channels formed therein. Electric contacts are provided inside each of the channels. Each channel can fit either a thermoelectric cooling device or a metallic block to provide different cooling profiles and design requirements. The cooling device is inserted between a liquid cooling plate and the chip to adjust and enhance heat transfer from the chip to the cooling plate. Alternatively, the cooling plate itself can serve as the housing with the channels, in which case the housing is provided with coupling for liquid pipes or hoses.

FIELD OF THE INVENTION

Embodiments of the present invention relate generally to cooling ofpackaged semiconductor devices. More particularly, embodiments of theinvention relate to cooling of heterogeneous packages of semiconductordevices.

BACKGROUND

Cooling is a prominent factor in a computer system and data centerdesign. The number of high performance electronics components such ashigh performance processors packaged inside servers has steadilyincreased, thereby increasing the amount of heat generated anddissipated during the ordinary operations of the servers. Thereliability of servers used within a data center decreases if theenvironment in which they operate is permitted to increase intemperature over time. Maintaining a proper thermal environment iscritical for normal operations of these servers in data centers, as wellas the server performance and lifetime. It requires more effective andefficient cooling solutions especially in the cases of cooling thesehigh performance servers.

Recent advancement in packaging of microchips includes heterogeneousintegration or heterogeneous packaging. Heterogeneous integration refersto the assembly and packaging of multiple separately manufacturedcomponents onto a single chip in order to improve functionality andenhance operating characteristics. Heterogeneous integration allows forthe packaging of components of different functionalities, differentprocess technologies (i.e., process nodes), different thermal propertiesand characteristics and sometimes separate manufacturers. The combineddevices can vary in functionality (e.g., processors, signal processors,cache, sensors, photonics, RF, and MEMS) and technologies (e.g., oneoptimized for die size with another one optimized for low power).

However, since each of the combined devices has different powerconsumption and heat dissipation characteristics, packaging them in asingle enclosure raises challenges to the thermal management of suchpackaging. In addition, the packaging may include auxiliary power unitswhich also have different heat dissipation characteristics. Therefore,the entire package may be in non-uniform thermal conditions duringnormal operation.

Furthermore, each of the packaged components may have different thermalspecifications/requirements, such as junction temperature or casetemperature for normal operation. It is critical to satisfy theserequirements for the thermal management solutions, especially when theserequirements are different for the various packaged devices.

A proper thermal design requires satisfying the thermal managementspecifications of all of the components within the heterogeneouspackage. Therefore, the design must account for the most temperaturesensitive component operating at peak power consumption, even if suchoperation takes place only occasionally.

The packaging locations and footprint of each device within the packageare mainly determined based on technical considerations other thanthermal management. The technical considerations may be based on, e.g.,actual topology, communication requirements, such I/O fabric distance,and so on. Therefore, the thermal design should be flexible sufficientlyto accommodate the package requirements.

On the other hand, providing different thermal management solution foreach different package increases cost and complexity of manufacturing. Astandard design or product is important for reducing the cost, as wellas for developing an ecosystem with multiple vendors. However, it is achallenge to have only one common product and specification to satisfydifferent type of heterogeneous packages and to solve the thermalchallenges mentioned.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 is a block diagram illustrating an example of a data centerfacility according to one embodiment.

FIG. 2 is a block diagram illustrating an example of an electronic rackaccording to one embodiment.

FIG. 3 is a block diagram illustrating an example of a cold plateconfiguration according to one embodiment.

FIGS. 4A and 4B are top view of a heat transfer device according to anembodiment, wherein FIG. 4A shows the device without heat transferelements and FIG. 4B illustrate the device with heat transfer elementsinserted.

FIG. 4C illustrates a front view of the thermal transfer deviceaccording to an embodiment.

FIGS. 5A and 5B illustrate the detailed function of the gap as well asits design requirement according to an embodiment.

FIGS. 5C-5E are cross-sections illustrating different embodiments forfabricating the encapsulation parts of the thermal transfer device.

FIG. 6 illustrates a diagram of a side view of system level integratedcomponent package using an embodiment of the heat transfer device.

FIG. 7 illustrates a diagram of a side view of system level integratedcomponents package using an embodiment of the heat transfer device.

FIG. 8 illustrates a diagram of a side view of system level integratedcomponents package using an embodiment of the heat transfer device thatis integrated into the cold plate.

FIG. 9 is a flow chart illustrating a process for fabricating thecooling device according to an embodiment.

DETAILED DESCRIPTION

Various embodiments and aspects of the inventions will be described withreference to details discussed below, and the accompanying drawings willillustrate the various embodiments. The following description anddrawings are illustrative of the invention and are not to be construedas limiting the invention. Numerous specific details are described toprovide a thorough understanding of various embodiments of the presentinvention. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofembodiments of the present inventions.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin conjunction with the embodiment can be included in at least oneembodiment of the invention. The appearances of the phrase “in oneembodiment” in various places in the specification do not necessarilyall refer to the same embodiment.

The current disclosure introduces a modular design and packaging methodusing thermoelectric cooling devices, which may solve the thermalproblems efficaciously. Aspects of the disclosure provide a modulardesign which may be used for cooling different types and designs ofpackages and provide thermal cooling for highly non-uniform power andthermal conditions in different locations in the heterogeneous package.

Disclosed embodiments provide a cooling layer that enables placement ofdifferent types of heat conductors at different locations on theheterogeneous package. The different heat conductors can be selectedaccording to the heat transfer requirements at different spatiallocations of the package. For example, a metallic block, such as acopper block, may be used at some locations, while a thermoelectriccooling (TEC) device can be used at locations requiring enhanced heatconduction.

Prior to discussing the particulars of different embodiments, thedescription provides some background regarding example environmentswhere the embodiments may be implemented. FIG. 1 is a block diagramillustrating an example of a data center or data center unit accordingto one embodiment. In this example, FIG. 1 shows a top view of at leasta portion of a data center. Referring to FIG. 1, according to oneembodiment, data center system 100 includes one or more rows ofelectronic racks of information technology (IT) components, equipment orinstruments 101-102, such as, for example, computer servers or computingnodes that provide data services to a variety of clients over a network(e.g., the Internet). In this embodiment, each row includes an array ofelectronic racks such as electronic racks 110A-110N. However, more orfewer rows of electronic racks may be implemented. Typically, rows101-102 are aligned in parallel with frontends facing towards each otherand backends facing away from each other, forming aisle 103 in betweento allow an administrative person walking therein. However, otherconfigurations or arrangements may also be applied. For example, tworows of electronic racks may back to back face each other withoutforming an aisle in between, while their frontends face away from eachother. The backends of the electronic racks may be coupled to the roomcooling liquid manifolds.

In one embodiment, each of the electronic racks (e.g., electronic racks110A-110N) includes a housing to house a number of IT componentsarranged in a stack operating therein. The electronic racks can includea cooling liquid manifold, a number of server slots (e.g., standardshelves or chassis configured with an identical or similar form factor),and a number of server chassis (also referred to as server blades orserver shelves) capable of being inserted into and removed from theserver slots. Each server chassis represents a computing node having oneor more processors, a memory, and/or a persistent storage device (e.g.,hard disk), where a computing node may include one or more serversoperating therein. At least one of the processors is attached to aliquid cold plate (also referred to as a cold plate assembly) to receivecooling liquid. In addition, one or more optional cooling fans areassociated with the server chassis to provide air cooling to thecomputing nodes contained therein. Note that the cooling system 120 maybe coupled to multiple data center systems such as data center system100.

In one embodiment, cooling system 120 includes an external liquid loopconnected to a cooling tower or a dry cooler external to thebuilding/housing container. The cooling system 120 can include, but isnot limited to evaporative cooling, free air, rejection to large thermalmass, and waste heat recovery designs. Cooling system 120 may include orbe coupled to a cooling liquid source that provide cooling liquid.

In one embodiment, each server chassis is coupled to the cooling liquidmanifold modularly, such that a server chassis can be removed from theelectronic rack without affecting the operations of remaining serverchassis in the electronic rack and the cooling liquid manifold. Inanother embodiment, each server chassis is coupled to the cooling liquidmanifold through a quick-release coupling assembly having a serverliquid intake connector and a server liquid outlet connector coupled toa flexible hose to distribute the cooling liquid to the processors. Theserver liquid intake connector is to receive cooling liquid via a rackliquid intake connector from a cooling liquid manifold mounted on abackend of the electronic rack. The server liquid outlet connector is toemit warmer or hotter liquid carrying the heat exchanged from theprocessors to the cooling liquid manifold via a rack liquid outletconnector and then back to a coolant distribution unit (CDU) within theelectronic rack. The CDU may also be a standalone unit instead ofpopulated on a server rack.

In one embodiment, the cooling liquid manifold disposed on the backendof each electronic rack is coupled to liquid supply line 132 (alsoreferred to as a room supply manifold) to receive cooling liquid fromcooling system 120. The cooling liquid is distributed through a liquiddistribution loop attached to a cold plate assembly on which a processoris mounted to remove heat from the processors. A cold plate isconfigured similar to a heat sink with a liquid distribution tubeattached or embedded therein. The resulting warmer or hotter liquidcarrying the heat exchanged from the processors is transmitted vialiquid return line 131 (also referred to as a room return manifold) backto cooling system 120.

Liquid supply/return lines 131-132 are referred to as data center orroom liquid supply/return lines (e.g., global liquid supply/returnlines), which supply cooling liquid to all of the electronic racks ofrows 101-102. The liquid supply line 132 and liquid return line 131 arecoupled to a heat exchanger of a CDU located within each of theelectronic racks, forming a primary loop. The secondary loop of the heatexchanger is coupled to each of the server chassis in the electronicrack to deliver the cooling liquid to the cold plates of the processors.Cold plate is widely used component for liquid cooling, although othertype of liquid cooling components may also connect to the liquid coolingsecondary loop.

In one embodiment, data center system 100 further includes an optionalairflow delivery system 135 to generate an airflow to cause the airflowto travel through the air space of the server chassis of the electronicracks to exchange heat generated by the computing nodes due tooperations of the computing nodes (e.g., servers) and to exhaust theairflow exchanged heat to an external environment or a cooling system(e.g., air-to-liquid heat exchanger) to reduce the temperature of theairflow. For example, air supply system 135 generates an airflow ofcool/cold air to circulate from aisle 103 through electronic racks110A-110N to carry away exchanged heat.

The cool airflows enter the electronic racks through their frontends andthe warm/hot airflows exit the electronic racks from their backends. Thewarm/hot air with exchanged heat is exhausted from room/building orcooled using a separate cooling system such as an air-to-liquid heatexchanger. Thus, the cooling system is a hybrid liquid-air coolingsystem, where a portion of the heat generated by a processor is removedby cooling liquid via the corresponding cold plate, while the remainingportion of the heat generated by the processor (or other electronics orprocessing devices) is removed by airflow cooling.

FIG. 2 is block diagram illustrating an electronic rack according to oneembodiment. Electronic rack 200 may represent any of the electronicracks as shown in FIG. 1, such as, for example, electronic racks110A-110N. Referring to FIG. 2, according to one embodiment, electronicrack 200 includes, but is not limited to, CDU 201, rack management unit(RMU) 202, and one or more server chassis 203A-203E (collectivelyreferred to as server chassis 203). Server chassis 203 can be insertedinto an array of server slots (e.g., standard shelves) respectively fromfrontend 204 or backend 205 of electronic rack 200. Note that althoughthere are five server chassis 203A-203E shown here, more or fewer serverchassis may be maintained within electronic rack 200. Also note that theparticular positions of CDU 201, RMU 202, and/or server chassis 203 areshown for the purpose of illustration only; other arrangements orconfigurations of CDU 201, RMU 202, and/or server chassis 203 may alsobe implemented. In one embodiment, electronic rack 200 can be eitheropen to the environment or partially contained by a rack container, aslong as the cooling fans can generate airflows from the frontend to thebackend.

In addition, for at least some of the server chassis 203, an optionalfan module (not shown) is associated with the server chassis. Each ofthe fan modules includes one or more cooling fans. The fan modules maybe mounted on the backends of server chassis 203 or on the electronicrack to generate airflows flowing from frontend 204, traveling throughthe air space of the sever chassis 203, and existing at backend 205 ofelectronic rack 200.

In one embodiment, CDU 201 mainly includes heat exchanger 211, liquidpump 212, and a pump controller (not shown), and some other componentssuch as a liquid reservoir, a power supply, monitoring sensors and soon. Heat exchanger 211 may be a liquid-to-liquid heat exchanger. Heatexchanger 211 includes a first loop with inlet and outlet ports having afirst pair of liquid connectors coupled to external liquid supply/returnlines 131-132 to form a primary loop. The connectors coupled to theexternal liquid supply/return lines 131-132 may be disposed or mountedon backend 205 of electronic rack 200. The liquid supply/return lines131-132, also referred to as room liquid supply/return lines, may becoupled to cooling system 120 as described above.

In addition, heat exchanger 211 further includes a second loop with twoports having a second pair of liquid connectors coupled to liquidmanifold 225 (also referred to as a rack manifold) to form a secondaryloop, which may include a supply manifold (also referred to as a rackliquid supply line or rack supply manifold) to supply cooling liquid toserver chassis 203 and a return manifold (also referred to as a rackliquid return line or rack return manifold) to return warmer liquid backto CDU 201. Note that CDUs 201 can be any kind of CDUs commerciallyavailable or customized ones. Thus, the details of CDUs 201 will not bedescribed herein.

Each of server chassis 203 may include one or more IT components (e.g.,central processing units or CPUs, general/graphic processing units(GPUs), memory, and/or storage devices). Each IT component may performdata processing tasks, where the IT component may include softwareinstalled in a storage device, loaded into the memory, and executed byone or more processors to perform the data processing tasks. Serverchassis 203 may include a host server (referred to as a host node)coupled to one or more compute servers (also referred to as computingnodes, such as CPU server and GPU server). The host server (having oneor more CPUs) typically interfaces with clients over a network (e.g.,Internet) to receive a request for a particular service such as storageservices (e.g., cloud-based storage services such as backup and/orrestoration), executing an application to perform certain operations(e.g., image processing, deep data learning algorithms or modeling,etc., as a part of a software-as-a-service or SaaS platform). Inresponse to the request, the host server distributes the tasks to one ormore of the computing nodes or compute servers (having one or more GPUs)managed by the host server. The compute servers perform the actualtasks, which may generate heat during the operations.

Electronic rack 200 further includes optional RMU 202 configured toprovide and manage power supplied to servers 203, and CDU 201. RMU 202may be coupled to a power supply unit (not shown) to manage the powerconsumption of the power supply unit. The power supply unit may includethe necessary circuitry (e.g., an alternating current (AC) to directcurrent (DC) or DC to DC power converter, battery, transformer, orregulator, etc.) to provide power to the rest of the components ofelectronic rack 200.

In one embodiment, RMU 202 includes optimization module 221 and rackmanagement controller (RMC) 222. RMC 222 may include a monitor tomonitor operating status of various components within electronic rack200, such as, for example, computing nodes 203, CDU 201, and the fanmodules. Specifically, the monitor receives operating data from varioussensors representing the operating environments of electronic rack 200.For example, the monitor may receive operating data representingtemperatures of the processors, cooling liquid, and airflows, which maybe captured and collected via various temperature sensors. The monitormay also receive data representing the fan power and pump powergenerated by the fan modules 231 and liquid pump 212, which may beproportional to their respective speeds. These operating data arereferred to as real-time operating data. Note that the monitor may beimplemented as a separate module within RMU 202.

Based on the operating data, optimization module 221 performs anoptimization using a predetermined optimization function or optimizationmodel to derive a set of optimal fan speeds for fan modules 231 and anoptimal pump speed for liquid pump 212, such that the total powerconsumption of liquid pump 212 and fan modules 231 reaches minimum,while the operating data associated with liquid pump 212 and coolingfans of the fan modules are within their respective designedspecifications. Once the optimal pump speed and optimal fan speeds havebeen determined, RMC 222 configures liquid pump 212 and cooling fans offan modules 231 based on the optimal pump speeds and fan speeds.

As an example, based on the optimal pump speed, RMC 222 communicateswith a pump controller of CDU 201 to control the speed of liquid pump212, which in turn controls a liquid flow rate of cooling liquidsupplied to the liquid manifold 225 to be distributed to at least someof server chassis 203. Similarly, based on the optimal fan speeds, RMC222 communicates with each of the fan modules to control the speed ofeach cooling fan of the fan modules 231, which in turn control theairflow rates of the fan modules. Note that each of fan modules may beindividually controlled with its specific optimal fan speed, anddifferent fan modules and/or different cooling fans within the same fanmodule may have different optimal fan speeds.

Note that the rack configuration as shown in FIG. 2 is shown anddescribed for the purpose of illustration only; other configurations orarrangements may also be applicable. For example, CDU 201 may be anoptional unit. The cold plates of server chassis 203 may be coupled to arack manifold, which may be directly coupled to room manifolds 131-132without using a CDU. Although not shown, a power supply unit may bedisposed within electronic rack 200. The power supply unit may beimplemented as a standard chassis identical or similar to a severchassis, where the power supply chassis can be inserted into any of thestandard shelves, replacing any of server chassis 203. In addition, thepower supply chassis may further include a battery backup unit (BBU) toprovide battery power to server chassis 203 when the main power isunavailable. The BBU may include one or more battery packages and eachbattery package include one or more battery cells, as well as thenecessary charging and discharging circuits for charging and dischargingthe battery cells.

FIG. 3 is a block diagram illustrating a processor cold plateconfiguration according to one embodiment. The processor/cold plateassembly 300 can represent any of the processors/cold plate structuresof server chassis 203 as shown in FIG. 2. Referring to FIG. 3, processorchip 301 is plugged onto a processor socket mounted on printed circuitboard (PCB) or motherboard 302 coupled to other electrical components orcircuits of a data processing system or server. Processor chip 301 alsoincludes a cold plate 303 attached to it, which is coupled to a rackmanifold that is coupled to liquid supply line 132 and/or liquid returnline 131. A portion of the heat generated by processor chip 301 isremoved by the cooling liquid via cold plate 303. The remaining portionof the heat enters into an air space underneath or above, which may beremoved by an airflow generated by cooling fan 304. In otherembodiments, the cold plate 303 can be in the form of other types ofcooling devices, such as air cooled heat sink, two phase cooling device,etc. For brevity, in the following description cold plate is used as anexample but each of the disclosed embodiments may be implemented usingany other cooling device.

In FIG. 3, when processor chip 301 is a heterogeneous package, the heatgenerated over the surface of the package is not uniform. Therefore, inFIG. 3 a heat transfer device 305 is inserted between the packagedprocessor chip 301 and the cold plate 303 to extract heat from thepackage 301 and transfer the heat to the cold plate 303 at differentrates over the surface of packaging 301. In disclosed embodiments theheat transfer device 305 is modular and can be fitted to differentpackaging having different thermal profile over their surface. Theexample of FIG. 3 illustrates the heat transfer device 305 as beingseparate from the cold plate 303; however, in other embodiments the heattransfer device 305 may be integral to the cold plate 303.

Disclosed embodiments provide composite structure utilizing heattransfer elements, including thermoelectric cooling devices, for thermalmanagement of heterogeneous packaged processors. One or multiplethermoelectric coolers are used in the thermal transfer devices,optionally in combination with other heat transfer elements, such ascopper blocks. A dedicated layer with specified spaces is used forassembling the heat transfer elements, e.g., thermoelectric coolers, toenhance the heat transfer from the packaged chip to the cold plate. Thethermal transfer device includes one or several specified spaces inwhich different thermal transfer elements can be inserted. Examplesinclude TEC unit or passive conduction copper block for different designtargets. Electrical connections are designed within each of the spacesfor powering any inserted TEC with DC power source. Insulators are usedfor multiple locations as well as on the copper blocks. A completecomposite packaging structure is disclosed.

The disclosed innovative structural design enables installing anddisassembling of one or more TEC units and copper blocks easily, andonce inserted, they are in good contact with the housing to eliminategaps, in order to ensure proper thermal management. In one embodiment,the layer can be designed as a separated unit packaging between thecooling device such as cold plate or heat sink and the heterogeneousASIC package. In other embodiments it can be integrated to the coolingdevice.

FIGS. 4A and 4B are top view of a heat transfer device according to anembodiment, wherein FIG. 4A shows the device without heat transferelements and FIG. 4B illustrate the device with heat transfer elementsinserted. As illustrated, the heat transfer device 400 has anencapsulation or housing 402 that includes multiple channels 405, whichmay be referred to as enhancing channels as they function to enhanceheat transfer. In this particular example, five channels 405 areillustrated, but any number of channels can be formed. These channels405 are used for inserting therein TEC units 410 and copper blocks 415in different combinations, depending on the particular heat transferrequirements. If the channel 405 is populated with TEC 410, thefootprint of the channel and TEC are aimed to fully or partially coverthe top of the surface of a special component requiring enhance heattransfer. The special component can refer to high power components, hightemperature sensitive components, components requiring better coolingconditions, component positioned in a location where it is not fullycovered by a cold plate main cooling area, and so on. When a regularblock 415 is used, it indicates that no enhanced cooling is need in adirection normal to the surface of the package in that location. Indisclosed embodiments the material of the heat transfer block 415 is thesame as the encapsulation 402 of thermal transfer device 400 so as notto degrade the heat transfer.

Electrical terminal pads 420 and 422, as well as electrical wires 424are pre-assembled within the thermal transfer device 400. Once a TEC 410is inserted, it is automatically connected to the electrical terminals420 and 422, and ready to receive DC power. The terminal pad haspositive side 420 and negative side 422 for each of the channels 405,such that each channel can be populated with TEC. An insulator 426 isshown on the bottom to isolate the encapsulation 402 from the powersource. An electrical port 428 is used to connect to external DC powersource. In one embodiment, the positive and native ports can be switchedor multiple power ports can be used to switch the cold side and hot sideof the TEC. When a copper block is inserted, it is insulated at the endsto prevent it from being connected to the electrical terminals.

FIG. 4B shows an assembled thermal transfer device wherein TEC 410 andpassive blocks 415 are inserted in the channels 405. In the particularexample illustrated, TEC 410 are inserted into the two end channels 405and solid blocks 415 are inserted in the middle three channels. Thisexample is specific to a situation wherein the two end regions of theheterogeneous package require enhanced heat transfer wherein thefootprint of the two TEC 410 covers the area occupied by the temperaturesensitive components. Of course this is but one example and the channels405 may be populated with different number and configuration of TEC andblocks as needed. Incidentally, an insulator 427 is needed on the blocksto insulate them from the electrical pads 420 and 422.

FIG. 4C illustrates a front view of the thermal transfer device 400according to an embodiment. In the illustrated example, the thermaltransfer device 400 is not yet fully assembled and no heat transferelements have been inserted in channels 405. As shown, in this conditiona very small gap exists between the upper portion and lower portion ofthe encapsulation 402. The gap 404 structure can be realized indifferent mechanical designs, e.g., machining the gap or making theencapsulation as two parts. This gap 404 is used for ease of insertingin or pulling out a TEC or block as needed. Thermal interface material(TIM) may be prefilled within the channel before any TEC or block isinserted to ensure proper heat conductivity.

As disclosed so far, the features introduced herein include modularityof design, ease of assembly, and uniform DC power connection. Modularityof design is enabled by the channels, wherein each channel may be loadedwith a TEC or a metallic block, to fit different specifications. Theclosable gap enables easy assembly and removal of TEC and metallicblocks when the gap is open, but then provides good thermal conductivitywhen the gap is closed. The TIM on the interior walls of the channelsalso help is good thermal conductivity. Universal DC connection isenables by having DC terminals in each channel, and having matingterminals on the TEC, so that the TEC is automatically connected to theDC terminals upon insertion into the channel. This enables uniformdesign of TEC terminals which can be used for any heterogeneouspackaging specification.

FIGS. 5A and 5B illustrate the detailed function of the gap as well asits design requirements according to an embodiment. FIG. 5A illustratesthe thermal transfer device 500 before assembling and fixing, while FIG.5B illustrates the thermal transfer device 500 after assembling andfixing with pressure loading. It can be seen that the gap 504 shown inFIG. 5A is closed in FIG. 5B when the unit is assembled and pressureloaded. To improve the heat conductivity of the device illustrated inFIGS. 5A and 5B the following may be implemented. The copper blocks andTEC are built to have the same dimensions, and in FIGS. 5A and 5B heighth presents the height of a TEC or a block.

For reducing manufacturing costs, the form factor of the TEC and blockis fixed. Height a represents the total height of the encapsulation 502before assembly and height al represents the height after assembly.Height b represents the height of the channel 505 before assembly andheight b1 represents the height after assembly, wherein height b1theoretically equals height h. Height d represents half the differencebetween the height b of the channel and height h of the TEC or block.Height c represents the height of the gap 504 before assembly. In thisposition theoretically c=2d, but in practice c is slightly smaller than2d. Theoretically heights c1 and d1 are zero after assembly; however, inpractice it is recommended that a TIM (thermal interface material) belined inside the channels to fill any gaps between the encapsulation andthe TEC or block after assembly.

As can be understood from FIG. 5A, the encapsulation 502 may befabricated in one machined part or two sections 502 a and 502 b. FIG. 5Cis a cross-section illustrating an embodiment wherein encapsulation 502is made of two mirror-image parts 502 a and 502 b. The parts can beassembled together while a resilient element 503, e.g., an O-ring,maintains the gap when no pressure is applied forcing the two sectionsto compress the resilient element and close the gap 504. Also, theinterior walls of channels 505 are lined with TIM 506 to provide betterthermal conductivity between the encapsulation and the heat transferelements. Additionally, DC terminals 520 and 522 are provide in eachchannel and are connected to electrical port 528. Consequently, there'sa single uniform design for connecting the TEC to DC power, and theconnection is achieved automatically upon insertion of a TEC into achannel. Specifically, the TEC is fabricated with electrical terminalsthat mate with terminals 520 and 522 upon insertion. Conversely, themetallic blocks are provided with insulation at the same physicallocation of the DC terminals, so that they do not short the terminals.

FIG. 5D is a cross-section illustrating an embodiment wherein theencapsulation 502 is made of two different parts. Specifically, in thisexample part 502 b forms a main block with channels 505. Part 502 aforms a lid, which may be in the form of a plate without any part of thechannels. Also, in this embodiment interior walls of cavities 505 arelined with TIM 506. The surface of the lid facing the main block 502 bis lined with TIM 507, which may be the same as TIM 506 or may be anadhesive TIM to adhere the lid to the main block 502 b.

FIG. 5E is a cross-section illustrating an embodiment whereinencapsulation 502 is made of a single block, e.g. machined out of ablock of copper. In this example, channels 505 and gap 504 are machinedout of the block, such that after insertion of the heat transferelements in the channels 505 the two sections 502 a and 502 b can becompressed together. This can be achieved by, e.g., creation of crumplezones 507, which may also function as a resilient element to return thegap to its original orientation after removal of compression force.

In the disclosed examples the parts of the encapsulation 502 are made ofthe same material as the blocks 415, e.g., copper. The interior walls ofthe channels 505 are lined with TIM. Once the thermal requirements ofthe chip to be cooled are understood, it is decided in which channel(s)505 a TEC will be inserted and in which a block will be inserted. Afterthe TEC and blocs have been inserted in the selected channels, the twosections are brought together and compressed to result in thearrangement shown in FIG. 5B. Note that the two sections can be broughttogether first as shown in FIG. 5A and then the TEC and blocks insertedin the respective channels.

FIG. 6 shows a diagram of a side view of system level integratedcomponent package using an embodiment of the heat transfer device 600.In this particular example TEC 610 is inserted in all of the channels605. The heat transfer device 600 is compressed between the cold plate603 and the heterogeneous package device 660. As illustrated in FIG. 6,since the TEC enhances the heat transfer from package 660 the cold plate603 may be smaller, having less heat transfer area while still satisfythe heat removal requirements.

FIG. 7 shows a diagram of a side view of system level integratedcomponents package using an embodiment of the heat transfer device 700.In this example, TEC 710 is inserted in the two end channels 705 andblocks 715 are inserted in the middle channels. This is done in order totransfer heat from the edges of the package 760 to the cold plate fasterthan in the center.

FIG. 8 illustrates an embodiment wherein the thermal transfer device 800is integrated with the cold plate 803 as one complete unit. In essence,the cold plate 803 forms the housing of the thermal transfer device 800,such that the channels 805 are formed directly in the cold plate 803.The cold plate may be liquid cooled via liquid coupling 808. In thisparticular example each of the channels is filled with a TEC.

Also illustrated in FIG. 8, and can be implemented in any of the otherembodiments albeit not illustrated, are electrical connections 870 fromthe electrical port 828 of the thermal transfer device 800 to themotherboard 801. Power may also be applied from other sources, buthaving the power from the mother board is convenient as it is close by.

FIG. 9 is a flow chart illustrating a process for fabricating thecooling device according to an embodiment. In block 900, anencapsulation is fabricated with channels and gap, according to any ofthe embodiments disclosed herein. In block 905 the electrical contactsand wiring is installed within the channels. In block 910 the interiorwalls of the channels are lined or coated with TIM. In block 915 one ormore TEC devices and one or more metallic blocks are inserted in thechannels, according to the heat transfer requirements of theheterogeneous package. During steps 900-915 the cooling device is notassembled yet within the cold plate and heterogeneous package, so thegap enables easy insertion of the TEC and metallic blocks. Also, whenthe TEC is inserted into one of the channels, it is automaticallyconnected to the electrical terminals within the channel. At block 920the encapsulation is compressed to close the gap. This can be donetogether with step 925, wherein the cooling device is assembled with theheterogeneous package and a cooling plate.

In the foregoing specification, embodiments of the invention have beendescribed with reference to specific exemplary embodiments thereof. Itwill be evident that various modifications may be made thereto withoutdeparting from the broader spirit and scope of the invention as setforth in the following claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

What is claimed is:
 1. A cooling device for a heterogeneous microchip,comprising: a housing made of thermal conductive material, the housinghaving a plurality of channels formed therein; electric contactsprovided inside each of the plurality of channels; at least onethermoelectric cooling device (TEC) inserted in one of the channels; andat least one metallic block inserted in one of the channels.
 2. Thecooling device of claim 1, wherein all of the plurality of channels havethe same dimensions.
 3. The cooling device of claim 2, furthercomprising thermal interface material provided on interior walls of thechannels.
 4. The cooling device of claim 2, wherein the housing furthercomprises a compressible gap formed among the channels.
 5. The coolingdevice of claim 4, wherein the compressible gap separates the housinginto two parts.
 6. The cooling device of claim 4, wherein a height ofthe channel less a height of the gap equals a height of the TEC.
 7. Thecooling device of claim 4, further comprising a resilient element tomaintain the gap in an open position.
 8. The cooling device of claim 2,further comprising direct-current (DC) electrical terminals providedwithin each of the plurality of channels.
 9. The cooling device of claim2, wherein the housing and the metallic block are made out of copper.10. A method for providing cooling to a server node having aheterogeneous chip, comprising: providing a cooling transfer devicehaving a plurality of channels formed therein; obtaining a heatdistribution specification of the heterogeneous chip and according tothe heat distribution specification, inserting at least onethermoelectric cooling (TEC) element in at least one of the channels,and inserting metallic blocks in remaining empty channels; and attachingthe cooling transfer device to the heterogeneous chip.
 11. The method ofclaim 10, further comprising installing electrical contacts in each ofthe plurality of channels, such that inserting the thermoelectriccooling (TEC) element in one of the channels automatically engages theelectrical contacts to supply DC power to the TEC.
 12. The method ofclaim 11, wherein attaching the cooling transfer device to theheterogeneous chip comprises compressing the cooling transfer devicebetween the heterogeneous chip and a cooing plate.
 13. The method ofclaim 12, wherein the cooling transfer device is provided with a gapintersecting the plurality of channels, and wherein compressing thecooling transfer device closes the gap.
 14. The method of claim 10,further comprising coating interior walls of the channels with thermalinterface material.
 15. The method of claim 10, further comprisingaffixing liquid coupling to the cooling transfer device.
 16. A servernode, comprising: a motherboard; a heterogeneous chip affixed to themotherboard; a heat transfer device attached to a lid of theheterogeneous chip, the heat transfer device comprising: a housing madeof thermal conductive material, the housing having a plurality ofchannels formed therein; electric contacts provided inside each of theplurality of channels; at least one thermoelectric cooling device (TEC)inserted in one of the channels; and, at least one metallic blockinserted in one of the channels.
 17. The server node of claim 16,further comprising leads connecting the electric contacts to themotherboard.
 18. The server node of claim 16, further comprising acooling plate attached on top of the housing.
 19. The server node ofclaim 16, further comprising thermal interface material provided oninterior walls of the channels.
 20. The server node of claim 16, furthercomprising cooling pipes coupled to the housing.